This invention relates generally to fuses and, more particularly, to fuses with indicators for opened fuse identification.
Fuses are widely used as overcurrent protection devices to prevent costly damage to electrical circuits. Fuse terminals typically form an electrical connection between an electrical power source and an electrical component or a combination of components arranged in an electrical circuit. A fusible link is connected between the fuse terminals, so that when electrical current flowing through the fuse exceeds a predetermined limit, the fusible link melts and opens the circuit through the fuse to prevent electrical component damage.
A large number of fuses for a given electrical system are typically contained within a fuse box, and an accompanying chart lists the particular electrical devices corresponding to the fuses contained in the box. After one or more of the fuses has opened, the chart must be reviewed to discover which particular electrical device or devices in the system are not working, and the chart must then be matched against the fuse box to locate the opened fuse or fuses. Aside from a fuse box chart, traditional fuses do not offer an adequate indicator to determine whether or not the fuse has opened. For fuse boxes that do not contain such a chart, in order to determine if a fuse has opened, or which fuse has opened, each individual fuse must be removed from the fuse box and tested or replaced, which is a monotonous, time consuming process that sometimes must be repeated before locating an opened fuse.
While some fuse indicators have been developed for use with cylindrical cartridge fuses, recent fuses have been developed which are rectangular in shape, such as a fuse described in commonly owned U.S. Pat. No. 5,841,337. Because the rectangular fuses are relatively new to the art, a fuse indicator is needed to accommodate these fuses.
Accordingly, it would be desirable to provide a less complicated and more reliable fuse indicating system that can accommodate both a cylindrical cartridge fuse and a rectangular fuse.
In an exemplary embodiment of the invention, an opened fuse indicator includes a fuse casing having a substantially transparent lens. A transparent base is positioned adjacent the window, and a sputtered metal deposition layer on the transparent base provides a light-colored conductive surface including a narrowed portion that forms a fuse link. The conductive sputtered metal layer is electrically connected to a pair of fuse terminals to form a secondary fuse circuit in parallel with a main fuse circuit. The sputtered metal layer melts away from the fuse link portion upon the occurrence of a fault condition that causes the main fuse circuit to open, thereby directing current into the secondary fuse circuit. A dark colored backing material is disposed adjacent the clear film so that the dark material may be seen through the transparent lens after the light colored material has melted. Thus, the fuse is indicated as opened when the light colored sputtered metal layer is no longer visible.